To meet the demand for wireless data traffic having increased since deployment of 4G (4th-Generation) communication systems, efforts have been made to develop an improved 5G (5th-Generation) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (COMP), reception-end interference cancellation and the like.
In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
Recently, due to the spread of wireless terminals supporting broadband multimedia services, such as smart phones, tablet Personal Computers (PCs) and the like, data traffic has increased exponentially in the wireless network. Since the number of users of the wireless terminals will further increase, and multimedia services provided using the wireless terminals will be further popularized, the data traffic in the wireless network is expected to increase much more than now. If even Machine to Machine (M2M) communication utilizing things (e.g., communication between things such as home appliances), which is a new communication service, is commercialized in addition to the typical communication services such as audio and video communication between users, the amount of data traffic that is processed by a Base Station (BS) or an evolved Node B (eNB) in the wireless network is predicted to increase dramatically, so the eNB may have difficulty in dealing with the higher levels of data traffic. Device to Device (D2D) communication has attracted much attention as one of the schemes for coping with the increase in data traffic in the wireless network.
The D2D communication has attracted attention in both the licensed band that is used in mobile communication and in the unlicensed band that is used by communication such as Wireless Local Area Network (WLAN). If the D2D communication is integrated with the existing mobile communication, it is noteworthy in that the traffic capacity of the eNB may increase and the overload of the eNB may be reduced. In D2D communication, after a D2D link for D2D communication is established between User Equipments (UEs) in the same cell or adjacent cells, the UEs may directly exchange data with each other via the D2D link without going through the eNB. In this case, it is possible to reduce two links (e.g., a link from a UE to an eNB, and a link from the eNB to another UE) to one link (e.g., a link from a UE to another UE), contribution to a reduction in the overload of the eNB.
In the meantime, for D2D communication, a process of setting up synchronization between devices is required. Generally, a terminal may set up synchronization based on the time information that is received from a synchronous base station or received through a Global Positioning System (GPS) receiver module in the terminal Therefore, in D2D communication, if synchronization is set up using the scheme of the related art, each device should access the synchronous base station or use the GPS receiver module, for synchronization setup.
In addition, depending on the type of the communication scheme supported in the communication system, the synchronous base station may not be supported, and if a device is located in a GPS shaded area (e.g., the space between the skyscrapers, the tunnel, the interior of the building, and the like), the device may not set up synchronization since the device cannot receive time information through its GPS receiver module. Eventually, if the device cannot use the synchronous base station or the GPS receiver module, the device of the related art may not even initiate the D2D communication.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.